The present invention concerns, especially, multi-station glass-forming machines, with each station provided with a deposit location at which the articles produced at that station are deposited. A common outfeed conveyor extends along the plural stations and carries produced articles away. Each station is provided with an article-transfer unit which, when activated, transfers articles from the respective deposit location onto the common outfeed conveyor. In the context of glass-producing machines, the article-transfer unit typically has the form of a pressure-fluid-activated cylinder-and-piston unit. The cylinder of the unit is swingable about a vertical swing axis. The piston of the unit carries an extendable-retractable push-off arm. When activated, the push-off arm extends, engaging behind the article to be transferred, whereupon the cylinder swings and the push-off arm moves the article onto the outfeed conveyor. Thereafter, the push-off arm retracts and the cylinder swings back to starting position.
One known multi-station glass-forming machine of this type comprises a main control shaft which mechanically controls the operation of the article-transfer units of the plural stations. The main control shaft drives an additional, auxiliary control shaft on which is adjustably carried a plurality of control cams, one for each station. Accordingly, all these control cams are rotated synchronously by the auxiliary control shaft. Before commencing actual machine operation, it is necessary that the angular position of each individual control cam be properly adjusted, and that the angular positions of all control cams be properly adjusted relative to one another, such that the operations controlled by the control cam occur in the proper sequence and with exactly correct timing. The angular positions or phases of the plural control cams must be staggered such that the article-transfer units at the stations of the multi-station glass-forming machine are activated in a sequence the same as the sequence in which glass gobs are being fed to the individual stations for article production. The individual control cams are all identical but, as already stated, must be preadjusted with regard to their respective angular positions on the auxiliary control shaft carrying them.
With conventional multi-station glass-forming machines of this type, it will often happen in operation that the series of glass articles transferred onto the common outfeed conveyor are observed not to be identically spaced one from the next. However, identical spacing of all articles on the common outfeed conveyor, irrespective of what stations they are coming from, is to be considered a prerequisite for optimum performance of whatever article-handling equipment is fed by the outfeed conveyor. Accordingly, in practice, if non-identical spacing develops in the articles transported on the common outfeed conveyor, it becomes necessary to disengage the auxiliary control shaft, hold it arrested and adjust the angular positions of one or more control cams appropriately. It is out of the question to safely attempt this adjustment with the auxiliary control shaft operating at full speed. Also, it is to be noted that non-identical spacing of the outfed articles can happen due to a variety of causes. For example, if one station of the machine is taken out of operation, this evidently will introduce a corresponding large gap into the series of articles on the conveyor. Likewise, because the operation of the plural article-transfer units may be somewhat different one to the next, then if the cams are adjusted to maintain identical article spacing at one conveyor-belt speed, these adjustments may have to be redone if the speed of the common outfeed conveyor is then changed. With the auxiliary control shaft thusly disengaged, no transfer of finished glass articles onto the outfeed conveyor can occur. Thus, it is also necessary to interrupt the feeding of glass gobs to the multi-station glass-forming machine, while adjusting the cams. This is self-evidently undesirable from the viewpoint of productivity. Additionally, thermal problems may arise; when machine operation is interrupted, the thermal equilibrium which the machine develops after steady operation is disturbed and, when glass begins again to be fed into the machine, faulty articles are produced until such time as thermal equilibrium is gradually reestablished. However, the worst of all the inconveniences in this typical prior-art approach is that, after all these adjustments have been made, the success of the adjustments can only be evaluated by starting the machine up again, and if further adjustment proves necessary--which will often be the case--then one must start all over.
Another shortcoming of the type of multi-station machine in question is that, because the plural article-transfer units are activated sequentially by their respective control cams, it is not possible, e.g., for test purposes, to activate all the article-transfer units in unison, i.e., to see which, if any, are operating differently from the others.
U.S. Pat. No. 4,007,028 to Bublitz et al. discloses a computerized multi-station glass-forming machine which, of course, must likewise provide the adjustabilities already present with cam-controlled machines of that type, but which seeks to do so by means quite different from cam-type control mechanisms. Each article-transfer or push-off unit of each station is driven by a pneumatic motor. The flow of pressurized air to the pneumatic motors is controlled by plural control valves which, in turn, are controlled by a computer, in a quite sophisticated way. The timing of the activation of the individual push-off units can be individually selected, i.e., each independent of the others, within certain limited time intervals and can be adjusted during operation of the multi-station machine by means of operator controls provided at a control panel. The system of that patent aims to provide extremely comprehensive control of the operations occurring, not only with respect to their timing, but with respect to their speeds, and other parameters, and is of very sophisticated, which is to say rather complex, character, compared to the cam-control systems more familiar to persons skilled in the art.